The following notes concern the four northern species that fall to unicolor (Kby.) in Horn's key to the species of Macrobasis (1885, Trans. Amer. Ent. Soc., XII, 110). These species are more or less confused in most collections, and while all have been described, there remains some confusion regarding their nomenclature. It appears that the name unicolor (Kby.) is preoccupied and that it must be replaced with the name murina (LeC.).